KEF celebrated its fiftieth anniversary a while ago and looked back with pride on half a century of technical innovations. In order to appreciate the Big 50, the KEF engineers created a very special speaker called LS50, whose concept was influenced by the legendary BBC studio monitor, the LS3/5a.
The LS3/5a was used as a their go-to monitor by the BBC for decades. Since its sound quality was exceptionally good, countless of copies of this speaker was made by other manufacturers - but the reference was always the BBC LS3/5a Monitor. If KEF was ever to launch a new project based on this legend, one must assume that the end result is a very special speaker indeed. The LS50 bookshelf speaker is a completely new design, with technical similarities to the current KEF Blade flagship floorstander. Add to that a good deal of brain power and sophisticated design solutions.
KEF’s mini-monitor is a compact bookshelf speaker in high-gloss black or white piano lacquer, which is equipped with a newly developed 5.25 inch Uni-Q array with a ‘rose gold’ magnesium-aluminum cone for the black version or ‘Electric Blue’ for the white. In the center of the driver sits a 1 inch aluminum dome tweeter with a ‘Tangerine Waveguide’. The latter contributes to the excellent, wide sound dispersion of the Uni-Q driver array. A large proportion of the phenomenal omnidirectionality of the KEF LS50 is due to the specially shaped midrange driver. The very flat membrane ensures that the sound waves of the tweeter isn´t negatively affected. In addition, the curved baffle provides optimized sound management and minimizes edge diffraction. Resonances are subdued by very effective bracing and stiffening of the cabinet. Eventual occurring residual resonances is kept inside the cabinet as the internal structure is separated from the outer structure by using insulation on critical parts of the cabinet. Perfect conditions to minimize discoloration in the midrange and allow the Uni-Q driver to play freely and openly at all frequencies.
The elliptically shaped bass reflex tube is flared generously at both ends, which handles and controls the flow behavior of the air exiting, thus avoiding flow noise and 'chuffing'. Another special feature distinguishing the bass reflex tube from being ordinary; in the middle of the tube sits a flexible section allowing the tube to expand, like a balloon or bicycle tube. The flexible port helps to eliminate long-stroke resonances that would otherwise cause discoloration in the midrange.
High and mid frequencies are filtered at about 2,200 hertz, and the minimum impedance is, according to KEF, at 3.2 Ohms. Our impedance measurements showed that the impedance dropped to a minimum of 3.8 Ohms in the lowest bass frequencies, which is why we would identify the LS50 as a 6-ohm speakers. The impedance curve indicates that it won´t cause any trouble, so even lower powered amplifiers should have no problem driving a pair of KEF LS50's. Amplifiers are connected to the anniversary speaker using the well dimensioned single-wiring terminals to which, depending on personal preference, banana plugs or stripped cable ends can be connected.
Build Quality & Finish
The KEF LS50 monitors are a perfect example of excellent workmanship and are technically absolutely up-to-date. The internal stiffening and the curved baffle make for a very stable and sturdy cabinet, which is insensitive to resonances. Weighing in at 15.8lbs each and finished with a high-gloss lacquer in either black or white it oozes quality, and the finish is flawless. Add to that no visible screws in the curved baffle as icing on the cake.
The KEF LS50 should definitely be treated to a generous break-in period – at least 24 hours – so that they can perform at their best. What these compact monitors can do is startling to say the least. Like very few other speakers, the LS50 will be able to exactly and unequivocally make clear whether the sound engineer has done a good job in the studio or not. If the singer is slightly off center, it is the work of the sound engineer – the compact KEF LS50 hides no details. Toed-in and aligned straight at the listener, it gave us an extremely clean and focused center stage in our listening room. In your own home you should experiment with the distance and toe-in a bit, until the sound ‘clicks’ – which is done very quickly thanks to the wide dispersion and homogeneity of the Uni-Q drivers.
The resolution of depth and width is extraordinary, voices sound natural and have exactly the right size and volume. Despite its small dimensions, the LS50 fills the listening room very convincingly with music. KEF's monitor speaker have an amazing stability to the sound and certainly has floorstander qualities - for a compact speaker with a 5.25 inch driver, this is more than remarkable. It can obviously not play really low bass, but down to 60-70 Hertz the LS50 sounds crisp and precise, without artificially adding anything. It sounds even larger when positioned near a wall while still looking great.
KEF monitors inspire with their plasticity, spatial acuity and their firm and clean sound image with excellent detail resolution. A real loudspeaker super star which time after time can give you spine-tingling experiences, particularly with vocal performances. KEF LS50 pairs accuracy with enthusiasm - they are the ideal speakers to make any type of music into an event.
The KEF LS50 gave their best in our 'Measurement Lab'. Although the frequency response is generally slightly uneven, overall everything was very well balanced and without any disturbing dips or peaks. The fairly compact monitor reached quite deep down into the bass frequencies, and easily reached our upper measurement limit at about 25,000 hertz. The 0-, 15- and 30-degree measurement showed a more or less straight line, which impressively demonstrate its phenomenal omnidirectional characteristics. The waterfall diagram shows the excellent decay and the THD chart confirmed the good-natured distortion behavior of the speaker.
KEF's anniversary model, the LS50, is a visually gorgeous speaker with equally glorious sound. Rarely has a compact mini-monitor of this size sounded so amazingly good like these speakers from KEF. And at this price - it´s and absolute recommendation!
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- LS50's unique technologies offer by far the cleanest, most accurate studio-grade performance of any mini monitor.
- Employs revolutionary technology developed for Blade, KEF's latest flagship loudspeaker.
- Using the very latest Uni-Q driver specifically designed for this model, LS50 radiates an extremely large listening area with remarkably fast, clean sound
- Matte black KEF logo atop a beautifully clad high gloss black speaker cabinet with 50th anniversary rose gold aluminium Uni-Q driver
- LS50 is one of the most award-winning speaker products ever released by KEF, by industry reviewers and consumers alike
|Design||Two-way bass reflex|
Uni-Q driver array:
HF: 25mm (1in.) vented
LF/MF: 130mm (5.25in.)
|Frequency range (-6dB)||47Hz - 45kHz|
|Frequency response (±3dB)||79Hz - 28kHz|
|Amplifier requirements||25 - 100 W|
2nd & 3rd harmonics (90dB, 1m)
|Nominal impedance||8Ω (min. 3.2Ω)|
Dimension (H x W x D)
302 x 200 x 278 mm
(11.9 x 7.9 x 10.9 in.)